﻿//-----------------------------------------------------------------------------
// Filename: G711Codecs.cs
//
// Description: G711 PCMU and PCMA codecs.
//
// Note: Copied verbatim from the NAudio project, 
// see https://github.com/naudio/NAudio.
//
// Author(s):
// NAudio Contributors
//
// History:
// 21 Apr 2020  Aaron Clauson   Copied code added to this project.
//
// License: 
// MS_PL Microsoft Public License.
//-----------------------------------------------------------------------------

namespace SIPSorcery.Media
{
    /// <summary>
    /// mu-law encoder
    /// based on code from:
    /// http://hazelware.luggle.com/tutorials/mulawcompression.html
    /// </summary>
    public static class MuLawEncoder
    {
        private const int cBias = 0x84;
        private const int cClip = 32635;

        private static readonly byte[] MuLawCompressTable = new byte[256]
        {
            0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
            4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
            5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
            5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
            6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
            6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
            6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
            6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7
        };

        /// <summary>
        /// Encodes a single 16 bit sample to mu-law
        /// </summary>
        /// <param name="sample">16 bit PCM sample</param>
        /// <returns>mu-law encoded byte</returns>
        public static byte LinearToMuLawSample(short sample)
        {
            int sign = (sample >> 8) & 0x80;
            if (sign != 0)
            {
                sample = (short)-sample;
            }

            if (sample > cClip)
            {
                sample = cClip;
            }

            sample = (short)(sample + cBias);
            int exponent = (int)MuLawCompressTable[(sample >> 7) & 0xFF];
            int mantissa = (sample >> (exponent + 3)) & 0x0F;
            int compressedByte = ~(sign | (exponent << 4) | mantissa);

            return (byte)compressedByte;
        }
    }

    /// <summary>
    /// A-law encoder
    /// </summary>
    public static class ALawEncoder
    {
        private const int cBias = 0x84;
        private const int cClip = 32635;

        private static readonly byte[] ALawCompressTable = new byte[128]
        {
            1, 1, 2, 2, 3, 3, 3, 3,
            4, 4, 4, 4, 4, 4, 4, 4,
            5, 5, 5, 5, 5, 5, 5, 5,
            5, 5, 5, 5, 5, 5, 5, 5,
            6, 6, 6, 6, 6, 6, 6, 6,
            6, 6, 6, 6, 6, 6, 6, 6,
            6, 6, 6, 6, 6, 6, 6, 6,
            6, 6, 6, 6, 6, 6, 6, 6,
            7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7,
            7, 7, 7, 7, 7, 7, 7, 7
        };

        /// <summary>
        /// Encodes a single 16 bit sample to a-law
        /// </summary>
        /// <param name="sample">16 bit PCM sample</param>
        /// <returns>a-law encoded byte</returns>
        public static byte LinearToALawSample(short sample)
        {
            int sign;
            int exponent;
            int mantissa;
            byte compressedByte;

            sign = ((~sample) >> 8) & 0x80;
            if (sign == 0)
            {
                sample = (short)-sample;
            }

            if (sample > cClip)
            {
                sample = cClip;
            }

            if (sample >= 256)
            {
                exponent = (int)ALawCompressTable[(sample >> 8) & 0x7F];
                mantissa = (sample >> (exponent + 3)) & 0x0F;
                compressedByte = (byte)((exponent << 4) | mantissa);
            }
            else
            {
                compressedByte = (byte)(sample >> 4);
            }

            compressedByte ^= (byte)(sign ^ 0x55);
            return compressedByte;
        }
    }

    /// <summary>
    /// a-law decoder
    /// based on code from:
    /// http://hazelware.luggle.com/tutorials/mulawcompression.html
    /// </summary>
    public class ALawDecoder
    {
        /// <summary>
        /// only 512 bytes required, so just use a lookup
        /// </summary>
        private static readonly short[] ALawDecompressTable = new short[256]
        {
            -5504, -5248, -6016, -5760, -4480, -4224, -4992, -4736,
            -7552, -7296, -8064, -7808, -6528, -6272, -7040, -6784,
            -2752, -2624, -3008, -2880, -2240, -2112, -2496, -2368,
            -3776, -3648, -4032, -3904, -3264, -3136, -3520, -3392,
            -22016, -20992, -24064, -23040, -17920, -16896, -19968, -18944,
            -30208, -29184, -32256, -31232, -26112, -25088, -28160, -27136,
            -11008, -10496, -12032, -11520, -8960, -8448, -9984, -9472,
            -15104, -14592, -16128, -15616, -13056, -12544, -14080, -13568,
            -344, -328, -376, -360, -280, -264, -312, -296,
            -472, -456, -504, -488, -408, -392, -440, -424,
            -88, -72, -120, -104, -24, -8, -56, -40,
            -216, -200, -248, -232, -152, -136, -184, -168,
            -1376, -1312, -1504, -1440, -1120, -1056, -1248, -1184,
            -1888, -1824, -2016, -1952, -1632, -1568, -1760, -1696,
            -688, -656, -752, -720, -560, -528, -624, -592,
            -944, -912, -1008, -976, -816, -784, -880, -848,
            5504, 5248, 6016, 5760, 4480, 4224, 4992, 4736,
            7552, 7296, 8064, 7808, 6528, 6272, 7040, 6784,
            2752, 2624, 3008, 2880, 2240, 2112, 2496, 2368,
            3776, 3648, 4032, 3904, 3264, 3136, 3520, 3392,
            22016, 20992, 24064, 23040, 17920, 16896, 19968, 18944,
            30208, 29184, 32256, 31232, 26112, 25088, 28160, 27136,
            11008, 10496, 12032, 11520, 8960, 8448, 9984, 9472,
            15104, 14592, 16128, 15616, 13056, 12544, 14080, 13568,
            344, 328, 376, 360, 280, 264, 312, 296,
            472, 456, 504, 488, 408, 392, 440, 424,
            88, 72, 120, 104, 24, 8, 56, 40,
            216, 200, 248, 232, 152, 136, 184, 168,
            1376, 1312, 1504, 1440, 1120, 1056, 1248, 1184,
            1888, 1824, 2016, 1952, 1632, 1568, 1760, 1696,
            688, 656, 752, 720, 560, 528, 624, 592,
            944, 912, 1008, 976, 816, 784, 880, 848
        };

        /// <summary>
        /// Converts an a-law encoded byte to a 16 bit linear sample
        /// </summary>
        /// <param name="aLaw">a-law encoded byte</param>
        /// <returns>Linear sample</returns>
        public static short ALawToLinearSample(byte aLaw)
        {
            return ALawDecompressTable[aLaw];
        }
    }

    /// <summary>
    /// mu-law decoder
    /// based on code from:
    /// http://hazelware.luggle.com/tutorials/mulawcompression.html
    /// </summary>
    public static class MuLawDecoder
    {
        /// <summary>
        /// only 512 bytes required, so just use a lookup
        /// </summary>
        private static readonly short[] MuLawDecompressTable = new short[256]
        {
            -32124, -31100, -30076, -29052, -28028, -27004, -25980, -24956,
            -23932, -22908, -21884, -20860, -19836, -18812, -17788, -16764,
            -15996, -15484, -14972, -14460, -13948, -13436, -12924, -12412,
            -11900, -11388, -10876, -10364, -9852, -9340, -8828, -8316,
            -7932, -7676, -7420, -7164, -6908, -6652, -6396, -6140,
            -5884, -5628, -5372, -5116, -4860, -4604, -4348, -4092,
            -3900, -3772, -3644, -3516, -3388, -3260, -3132, -3004,
            -2876, -2748, -2620, -2492, -2364, -2236, -2108, -1980,
            -1884, -1820, -1756, -1692, -1628, -1564, -1500, -1436,
            -1372, -1308, -1244, -1180, -1116, -1052, -988, -924,
            -876, -844, -812, -780, -748, -716, -684, -652,
            -620, -588, -556, -524, -492, -460, -428, -396,
            -372, -356, -340, -324, -308, -292, -276, -260,
            -244, -228, -212, -196, -180, -164, -148, -132,
            -120, -112, -104, -96, -88, -80, -72, -64,
            -56, -48, -40, -32, -24, -16, -8, -1,
            32124, 31100, 30076, 29052, 28028, 27004, 25980, 24956,
            23932, 22908, 21884, 20860, 19836, 18812, 17788, 16764,
            15996, 15484, 14972, 14460, 13948, 13436, 12924, 12412,
            11900, 11388, 10876, 10364, 9852, 9340, 8828, 8316,
            7932, 7676, 7420, 7164, 6908, 6652, 6396, 6140,
            5884, 5628, 5372, 5116, 4860, 4604, 4348, 4092,
            3900, 3772, 3644, 3516, 3388, 3260, 3132, 3004,
            2876, 2748, 2620, 2492, 2364, 2236, 2108, 1980,
            1884, 1820, 1756, 1692, 1628, 1564, 1500, 1436,
            1372, 1308, 1244, 1180, 1116, 1052, 988, 924,
            876, 844, 812, 780, 748, 716, 684, 652,
            620, 588, 556, 524, 492, 460, 428, 396,
            372, 356, 340, 324, 308, 292, 276, 260,
            244, 228, 212, 196, 180, 164, 148, 132,
            120, 112, 104, 96, 88, 80, 72, 64,
            56, 48, 40, 32, 24, 16, 8, 0
        };

        /// <summary>
        /// Converts a mu-law encoded byte to a 16 bit linear sample
        /// </summary>
        /// <param name="muLaw">mu-law encoded byte</param>
        /// <returns>Linear sample</returns>
        public static short MuLawToLinearSample(byte muLaw)
        {
            return MuLawDecompressTable[muLaw];
        }
    }
}
